Shrink Tunnel A shrink tunnel also known as a heat tunnel is a heated tunnel that is mounted over a conveyor belt. A shrink tunnel is used to employ the heat shrinking technique for wrapping a package. A shrink tunnel can be semi-automatic or automatic. Working A shrink tunnel machine involves a conveyor and heat to maintain constant temperatures inside the tunnel chamber. The shrink film tends to alter the irregular arrangement of the original molecules when heated. Under the thermal radiation of steam or infrared rays, the plastic molecules are again arranged closely, which results in the reduction of the original area of the plastic, and gets closely attached to the product surface to achieve tight and secured packaging.